1. Field of the Invention
The present invention relates to a valve operating system for an internal combustion engine and, in particular, to an electromagnetic type valve operating system, that includes an armature operatively connected to an engine valve, a valve-opening electromagnet for exhibiting an electromagnetic force for attracting the armature to open the engine valve, a valve-closing electromagnet for exhibiting an electromagnetic force for attracting the armature to close the engine valve, a valve-opening resilient means for exhibiting a resilient force for biasing the engine valve in a valve opening direction, and a valve-closing resilient means for exhibiting a resilient force for biasing the engine valve in a valve closing direction and for maintaining the armature at a predetermined neutral position by cooperation with the valve-opening resilient means during deenergization of the valve-opening and valve-closing electromagnets.
2. Description of the Related Art
Such a valve operating system is conventionally known, for example, from PCT International Patent Application Laid-open No. WO95/00959 and the like.
In such a valve operating system, the engine valve is in the neutral position when both the electromagnets are in their non-energized states. The armature is attracted to the valve-opening electromagnet by supplying an electric current to the valve-opening electromagnet to open the engine valve, and the armature is attracted to the valve-closing electromagnet by supplying the electric current to the valve-closing electromagnet to close the engine valve. To provide an enhancement in performance of the engine, it is desirable that an efficient magnetic circuit is formed between the armature and the valve-opening and valve-closing electromagnets, so that the electromagnetic attracting forces provided by the valve-opening and valve-closing electromagnets are increased.